s1 = 'Foo'
s2 = 'Boo'
s3 = 'Foo'
s4 = 'Duh'
s = "We have a collection of types {}."
lst = [s1,s2,s3,s4]
fin = []
for x in lst:
if x not in fin:
fin.append(x)
print(s.format(", ".join(fin)))
czEgPSAnRm9vJwpzMiA9ICdCb28nCnMzID0gJ0ZvbycKczQgPSAnRHVoJwpzID0gIldlIGhhdmUgYSBjb2xsZWN0aW9uIG9mIHR5cGVzIHt9LiIKbHN0ID0gW3MxLHMyLHMzLHM0XQpmaW4gPSBbXQpmb3IgeCBpbiBsc3Q6CglpZiB4IG5vdCBpbiBmaW46CgkJZmluLmFwcGVuZCh4KQpwcmludChzLmZvcm1hdCgiLCAiLmpvaW4oZmluKSkp